Ethylene and propylene petrochemicals have been traditionally produced through thermal cracking also known as steam cracking, using petrochemical naphtha as a predominant feed. The ACO technology, on the other hand, relies on catalytic cracking for ethylene and propylene production with a much higher propylene to ethylene (P/E) ratio, typically around 1:1, more than doubling that produced through steam cracking. This high performance is seen even when using the same common petrochemicals feed such as straight run Naphtha. Thus ACO can provide additional flexibility and benefits to many producers who already use petrochemical naphtha feeds to produce ethylene. Another added benefit is that ACO has a much lower carbon footprint than steam cracking. Simply put, the use of catalyst in the reaction lowers the temperature at which olefins are formed thus lowering the level of fuel firing and CO2 emissions.
ACO™ technology licensor, KBR, combines Orthoflow™ fluidized catalytic cracking reactor system with a proprietary catalyst, developed by SK energy in Korea, which selectively converts straight run paraffinic feeds to large quantities of FCC propylene and ethylene. The ACO reactor system includes the Orthoflow configuration with dual riser, closed cyclones, third stage separator, patented catalyst well for continuous fuel firing, and patented catalyst removal system.
The ACO catalytic cracking process makes about 15-25% more ethylene plus propylene on a relative basis, depending on the operating conditions, compared to a thermal cracker. Further, the ACO process has a higher concentration of BTX in the gasoline fraction, resulting in about 20-25% higher absolute aromatics yield from the ACO process.
Comparing the Cost of Production (COP) of ethylene from the ACO catalytic cracker to a steam cracker clearly demonstrates the value of ACO technology. In this type of analysis, an ethylene plant's feed and operating costs are offset by the byproduct values. Other costs include indirect and overhead costs and depreciation (10%) and profit is added (10%) to arrive at an overall COP. Based upon a constant feed rate, the ACO process is favored over steam cracking by lower COP of about $90/MT of ethylene in early 2008.
Features of ACO Technology
KBR's ACO technology features unique and innovative design aspects to address the fact that the petrochemical feeds to these units are much lighter than in a traditional refinery FCC. These patented, commercially demonstrated design features include:
The ACO process produces both polymer grade ethylene and propylene. Much of the product recovery flow scheme is similar to typical olefins plant recovery sections; however, there are some unique features. For example, there are trace impurities such as nitrogen oxides, oxygen, and other trace impurities by virtue of the FCC-type reactor that must be removed. These and other issues are addressed in the ACO process flow scheme, which features all the advantages of KBR's depropanizer-first flow scheme including:
For more information on Advanced Catalytic Olefins (ACO™) Technology, please visit our KBR Petrochemicals publications.